1. Field of the Disclosure
This specification relates to a door interlock device for a vacuum circuit breaker, and more particularly, a door interlock device for a vacuum circuit breaker, which is operable in cooperation with an operation of a cradle shutter.
2. Background of the Disclosure
In general, a vacuum circuit breaker is a type of circuit breaker, which is installed in a high-pressure power system to break a circuit upon an occurrence of dangerous situations, such as short-circuit or overcurrent, so as to protect the power system. The vacuum circuit breaker is designed by utilizing high insulating performance and arc extinguishment in a vacuum state. That is, the vacuum circuit breaker is a product of protecting lives and load devices by breaking a circuit in a vacuum interrupter (VI) provided therein in a vacuum-extinguishing manner by an external relay when a fault current, such as overcurrent, short-circuit, earth fault current or the like, is generated on a super-high-pressure/high-pressure power distribution line.
The vacuum circuit breaker is generally installed in a switchboard in which various electric devices including a circuit breaker are placed and managed for operation or control of a power generator and a substation, an operation of a motor and the like. The vacuum circuit breaker is used by being accommodated in a cradle fixed to the switchboard.
The cradle has therein a service position (location) at which a terminal of the vacuum circuit breaker is connected to a terminal of the cradle to allow for the supply of voltage and current, and a test position at which the terminal of the vacuum circuit breaker is disconnected from the terminal of the cradle so as to allow only for testing an operation of the circuit breaker.
As the prior art of the door interlock device for the vacuum circuit breaker, the Korean Registration Patent No. 10-1168083 titled ‘Door lock device and circuit breaker using the same’ will be referred to. FIGS. 1A to 3 illustrate a technology disclosed in the prior document.
FIG. 1A is a view illustrating an open state of a door at a test position of a vacuum circuit breaker according to the related art, FIG. 1B is a view illustrating a closed state of the door at a service position of the vacuum circuit breaker according to the related art, and FIG. 2 is a detailed view of a door interlock device of FIG. 1B.
A door assembly 110 is attached to a cradle 100. A vacuum circuit breaker main body 200 may be inserted into the cradle 100. The vacuum circuit breaker main body 200 is loaded on a truck 210 to be conveyed to the service position or the test position or drawn out of the cradle 100. When the vacuum circuit breaker main body 200 is located at the service position, a main body terminal 201 of a main circuit part 205 is coupled to a cradle terminal 101 such that high voltage and current are applied.
An interlock plate 111 is installed on the door assembly 110 to be rotatable centering on a rotation shaft 113, and a guide groove 112 is formed at the interlock plate 111.
A door interlock device 300 is provided in an upper portion of the cradle 100 to fix the door assembly 110.
Hereinafter, a detailed configuration of the door interlock device 300 will be described with reference to FIG. 2. A rotation shaft 301 is provided on one side portion of a base plate 305. A rotation plate 302 in a shape like an alphabet “L” is coupled to the rotation shaft 301. One end portion 302a of the rotation plate 302 extends downward, and a locking bar 303 is provided on the other end portion 302b of the rotation plate 302. A return spring 304 is installed on the locking bar 303.
FIG. 3 illustrates the vacuum circuit breaker main body 200 according to the related art. An interlock driving plate 203 is provided on an upper portion of a front cover 202 of the vacuum circuit breaker main body 200.
The door interlock device according to the related art operates in the following manner.
A key is inserted into a key lock 114 of the door assembly 110 and turns the interlock plate 111 in a counterclockwise direction for release, thereby closing the door assembly 110 on the cradle 100.
The truck 201 is driven to convey the vacuum circuit breaker main body 200 to the service position. When the vacuum circuit breaker main body 200 is completely moved to the service position, the interlock driving plate 203 of the front cover 202 pushes the one end portion 302a of the rotation plate 302 of the door interlock device 300. Accordingly, the rotation plate 302 is rotated centering on the rotation shaft 301. In response to the rotation of the rotation plate 302, the locking bar 303 provided on the other end portion 302b of the rotation plate 302 is moved downward.
During this, the interlock plate 111 is rotated and thus the guide groove 111 is inserted into (or engaged with) the locking bar 303. Since the locking bar 303 fixes the interlock plate 111 coupled to the door assembly 110, the opening of the door assembly 110 is restricted (the door assembly 110 is locked).
For unlocking the door assembly 110, the key (not illustrate) is inserted into the key lock 114 and rotates the interlock plate 111 in a clockwise direction so as to release the interlock plate 111 from the locking bar 303. Accordingly, the door assembly 100 can be open.
However, the operation of the door interlock device according to the related art is performed through such complicated sequential processes of releasing the interlock plate 111 using the key, closing the door assembly 110, conveying the vacuum circuit breaker main body 200, and closing the interlock plate 111 again. When one of those complicated processes is omitted or the operating order of those processes changes, the locking of the door assembly 110 may not be carried out properly and related components may be damaged. This may result in operator's inconvenience in view of the requirement for the operator's attention.
In addition, the interlock device 300 operates only when the vacuum circuit breaker main body 200 is located at the service position. Therefore, the prevention of opening (or the locking of) the door assembly 110 is failed during insertion and withdrawal of the vacuum circuit breaker main body 200.